The president isn't the only one having trouble defining sex lately. With all the hanky panky going on in cyberspace, who knows what constitutes infidelity anymore? Happily married person meets who knows what in a chat room. Chat leads to private messages, which leads to intimate emails, which leads to tumescent phone calls. Even if it doesn't culminate at the Shady Inn, there comes a point at which the argument that cybersex isn't sex begins to melt down. The extent to which cybersex is affecting real sex, along with real marriages, families and other relationships, has become a subject of hot speculation, but mostly anecdotal evidence, much of which can be found online.

At "Self-Help & Psychology Magazine" <www.cybertowers.com/selfhelp>, Marlene M. Maheu, Ph.D. and Kristin Levine are conducting a survey on "CyberRomance: CyberRelationships and CyberSex" for a forthcoming book. Of the thousand people who have filled out their online survey so far, about half answered "yes" to "Are cyber-sexual affairs safer than physical ones?" Seventy percent said they knew someone who has had a "cyber affair," and another 70 percent answered "yes" or "sometimes" to "Is cybersex a threat to traditional relationships?"

What is this thing called cyber love? According to "Cyber Romance 101" <web2.airmail.net/~walraven/rom.htm>, there is no one answer. But the site is a primer for cyber relationships, with links to books, articles, advice columnists, psychologists, studies, fiction and first-person accounts of cyber lust.

"The Center for Online Addiction" <www.netaddiction.com> claims to be "the World's First Consultation Firm and Virtual Clinic for Cyber-Related Issues." It is run by Kimberly S. Young, a clinical psychologist and self-described "cyberpsychologist" who has also written a book, "Caught in the Net: How to Recognize the Signs of Internet Addiction and A Winning Strategy for Recovery." Young estimates that "1 in 5 Internet addicts are engaged in some form of on-line sexual activity," and that while men are more likely to look at cyberporn, women are more likely to engage in cybersex.

The site has tests you can take to find out whether you have an Internet or cybersexual addiction. Symptoms include "hiding your on-line interactions from your significant other," "feeling guilt or shame from your on-line use," and "frequently using anonymous communication to engage in sexual fantasies not typically carried out in real-life."

"Cybersociology Magazine" <www.socio.demon.co.uk/magazine/magazine.html> devoted its first issue to "Cybersex and Cyber-Romance." Some of the articles are scholarly, such as "Researching Cybersex in Online Chat Rooms: the Ethnographic Approach," by site editor Robin Hamman. But there's also a personal account of an email romance and cybersex by a woman with a physical disability, and "Cyber-Charade," free verse by "Cara" <www.geocities.com/SoHo/Studios/5116/index.html>, who describes the feelings and emotions of cybersex participants.

One of her poems, "Intimate Strangers," begins: "Whirling through endless electronic realms/ You launched your lust upon electric currents/ Of cresting cybercircuits, wanting a fantasy,/ A lover who would create a magic moment,/ A mystery-space in time, oblivious as to why,/ Escape into a virtual world of intimacy."

Finally, there's "Lust in Space" <www.cyberg8t.com/charlie/main.htm>, "for those intrigued, fascinated, lured, and otherwise 'hooked' on the interdimensional relationships that evolve on this new horizon of cyberspace." It is operated by "PlatypusMan" and "Looseal," who met in a chat room, and Looseal's best friend "Vixen," who enjoys computer role-playing games.

The site says there are two schools of thought on whether having an online relationship is cheating on your spouse. One is that it's not cheating because there is no physical relationship. The other is that "if you give your mind to another, then you have given more of yourself than if you had physical contact. Giving your love and emotions to another can be viewed as the ultimate act of cheating. Take your choice. Whatever works for you."

Cyber relationships can affect real life relationships and threaten even the most stable of marriages. But cyber affairs don't always work out either. First of all, there's "cyber infidelity," which is when someone in a cyber relationship begins cybering with someone new. "Oddly enough," the site says, "most people in a cyber relationship whose online love has a Real World significant other, don't get jealous of the Real World relationship. It is the cyber cheating that causes the pain." And cyber lovers who become real world lovers often get suspicious if their partners still go online. "It's no different than people who meet in the Real World," it says. "Trust is the key issue."